The Solar Impulse's Across America tour will kick off this May when founders Bertrand Piccard and André Borschberg take off from San Francisco

The Solar Impulse is the world’s first airplane to fly both day and night without fuel. There’s a lot of engineering behind this incredible feat – the plane’s wingspan is the size of an Airbus A340 (208 feet), yet it weighs less than a small car (3,527 pounds). Pilot André Borschberg said that the ratio of weight to wingspan is about equivalent to that of a hang glider.

The plane’s ultralight carbon fiber skeleton is held aloft by two wings clad with 12,000 solar panels strung into groups of 300 cells. These photovoltaics capture the sun’s energy throughout the day and use it to drive the plane’s four 10-horsepower engines. Excess energy is stored in 4 lithium polymer batteries that provide backup power for night flights. The plane’s average speed clocks in at 43 miles per hour, and it runs on about as much power as a tiny motor scooter.

Photos by Mike Chino for Inhabitat

The Solar Impulse’s Across America tour will kick off this May when founders Bertrand Piccard and André Borschberg take off from San Francisco. From there the plane will visit four cities across the states – Phoenix, Dallas, either Atlanta, Nashville or St. Louis (TBD), and Washington, DC – before finishing its tour in New York.

The team chose to limit each day’s flight time to less than 24 hours, although theoretically the plane could stay aloft indefinitely – after completing its first day and night flight the Solar Impulse still had 40% of its battery life remaining. The plane’s total battery capacity is about equivalent to a fully loaded Tesla Roadster, and it’s capable of simultaneously charging its batteries and driving its electric motors while in flight.

Piccard and Borschberg plan to stop at schools and host live in-flight conversations to spread the Solar Impulse’s spirit of innovation and show the power of green technology. Piccard said “Once you start to love the unknown, life starts to be a fantastic adventure – and this is what the solar impulse is all about”

Photos by Mike Chino for Inhabitat

After the Solar Impulse completes its journey across the United States this July, the team will devote all of their energy to preparing for the project’s trip around the world in 2015. The rigors of intercontinental travel demand a newly designed airplane dubbed the HB-SIB, which will feature updated, cutting-edge components and systems, isolated electrical circuitry that can withstand rain, and more cabin space for sleeping during flights up to 5 days long.

The Solar impulse was developed with the help of over 80 partners including Solvay, which provided the plane’s batteries and other components; Bayer, which provided insulation; Schindler, which provided energy-efficient technology; California-based Sunpower, which provided the plane’s thin-film photovoltaics; and Swiss Re, which insured the airplane and allowed it to take the risks that it does. The Solar Impulse project was designed in collaboration with the Ecole Polytechnique de Lausane.

Not the first. The first attempt was Greg Raymond in 1992. Lack of funding made the journey inoperable, not unlike many of these innovative ideas in the 90’s. Greg easily flew the SunSeeker up and down CA. It had space-grade cells and state of the art nickel cadmium batteries. Pic: http://www.automorrow.com/solplane.jpg